Thermomagnetic control apparatus



Nov. 30, 1965 c, s, oc m ETAL 3,220,463

THERMOMAGNETIC CONTROL APPARATUS Filed Nov. 1, 1962 2 sheets-sheet 1 jsrg 2 36A... 38b F 6'. 3 37b INV T R; /56 /6b ggw ATVOP/VE) United States 3,220,463 THERMOMAGNETIC CONTROL APPARATUS Colin Stanley Hocking, Bromma, and Nils Lennart Hultgren, Stockholm, Sweden, assignors to Aktiebolaget Electrolux, Stockholm, Sweden, a corporation of Sweden Filed Nov. 1, 1962, Ser. No. 234,793 Claims priority, application Sweden, Nov. 8, 1961,

11,131/ 61 4 Claims. (Cl. 158-132) Our invention relates to ther'momagnetically powered control apparatus. More particularly, the invention relates to thermomagnetically powered apparatus which is embodied in a flow interrupter for shutting off the supply of fluid fuel to a burner when the burner flame is extinguished.

It is an important object of our invention to provide improved control apparatus which effects one or several control operations in accordance with the energization and de-energization of the source of power which is embodied in the apparatus and functions as a thermomagnetically powered unit.

Another object of our invention is to provide improved control apparatus of this type having coacting relatively movable thermomagnetic and permanent magnet member biased toward a retracted position and movable to an attracted position when the temperature of the thermomagnetic member exceeds a critical temperature, at which time it becomes strongly magnetic and establishes a magnetic field, there being a control member operatively associated with the permanent magnet member and movable between the attracted and retracted positions with respect thereto.

A further object of our invention is to provide an improved control system which utilizes any intermittent source of heat and resulting heating and cooling periods to modify the output of a thermomagnetically powered unit for one or more operations to be performed by the control apparatus.

A still further object of our invention is to provide a new and improved flow interrupter which embodies a thermomagnetically powered unit to close a magnetically responsive valve and shut off flow of fuel to a burner.

A still further object of our invention is to provide an improved flow interrupter of this type having a relatively small powered unit which is capable of establishing a magnetic field of sufficient strength to move the valve from its closed position to its open position responsive solely to increase in temperature of a component of the thermomagnetically powered unit.

The novel features which we believe to be characteristic of our invention are set forth with particularity in the claims. The invention, both as to organization and method, together with further objects and advantages thereof, will be better understood by reference to the following description taken in connection with the accompanying drawings, of which:

FIG. 1 more or less diagrammatically illustrates a vertical section of control apparatus embodying the invention;

FIGS. 2, 3 and 4 are vertical sectional views of control apparatus like that shown in FIG. 1 illustrating modifications of the invention; and

FIGS. 5, 6 and 7 are fragmentary vertical sectional views of control apparatus generally like that shown in FIGS. 1, 2 and 4 illustrating still further modifications of the invention.

Referring to FIG. 1, we have shown our invention in connection with a burner 10 which includes a body member 11 having an inlet 12 which is adapted to be connected to a conduit of a fluid fuel supply line. Fluid fuel supplied to the inlet 12 flows to a chamber 14 through pas- 3,220,463 Patented Nov. 30, 1965 sages 15 and 16 which are perpendicular to one another. The flow of fluid fuel through passages 15 and 16 is controlled by a valve 17 which forms part of a safety cut-off apparatus to be described hereinafter.

The body 11 is formed with an outlet 18 through which fluid fuel flows from chamber 14, the outlet functioning as an orifice through which fluid fuel is discharged into a mixing chamber 19 formed in the lower end of a burner tube 20 which is secured to the body member 11. The lower end of burner tube 20 is provided with a plurality of ports or openings 21 to admit primary air into chamber 19. The primary air mixes with fluid fuel introduced into chamber 19 to provide a combustible gas mixture. The gas mixture formed in chamber 19 flows upward through the burner tube 20 and is discharged at an opening 22 at which region the burner flame is produced and maintained.

If for any reason the burner flame is extinguished, it is desirable to shut off the flow of fluid fuel to the burner 10. This is accomplished by providing a safety cut-off apparatus including the valve 17 in chamber 14 which is urged or biased to its closed position by a coil spring 23. The upper end of a rod or pin 24 bears against the valve 17 to move the latter to its open position against the action of coil spring 23. The rod 24 extends through an opening in a cap screw 25 and is provided at its outer end with an operating member 26. A suitable packing 27 is provided about the rod 24 at the upper end of chamber 28 to prevent leakage of fluid fuel through an opening 29 through which the rod extends. A coil spring 30 in chamber 28 is disposed about the rod 24, the upper end of which bears against the packing 27 and the lower end of which bears against a washer 31 fixed to the rod 24. The rod 24 is biased downward by the coil spring 30, and, when the operating member 26 is pushed upward, upward movement is imparted to the rod 24 against the biasing action of the spring 30.

In accordance with our invention, in order to maintain valve 17 in its open position during operation of the burner 10, we provide thermomagnetic control apparatus which functions as a safety cut-off and comprises a magnetically permeable member 32 and a thermomagnetic member 33 which becomes magnetic when the temperature thereof comes up to a predetermined temperature level and which becomes essentially non-magnetic when the temperature thereof drops below the predetermined level. The opposing faces of the members 32 and 33 are recessed to receive the ends of the coil spring 23 which biases the member 32 toward a retracted position separated from the member 33.

A body 34 of resilient material, such as natural or synthetic rubber, for example, is fixed to the bottom side of the member 32 and functions as a valve sealing means. The resilient body 34 and permanent magnet 32 together form the valve 17 which, in the retracted position shown in FIG. 1, is in its seated position and shuts off flow of fuel to the burner tube 20. Pushing the button 26 of the rod 24 upward imparts upward movement to the valve 17 against the biasing action of the coil spring 23.

In order that the thermomagnetic member 33 will be responsive to the heat of fuel burned at the opening 22 of burner tube 20, we provide an elongated heat conductor 35 formed of any suitable material having good heat conductivity, one end 35' of which is heat conductively connected to the member 33 and the other outer free end 35" of which is positioned at the vicinity of the burner flame. The outer end 35" of the heat conductor 35 functions as a heat receiving element from which heat flows to the member 33. The heat conductor 35 is enveloped in insulation 36 which extends from its inner end 35' to a region removed from its outer free end 35".

A cap screw 37 firmly holds the insulation 36 about the inner end 35' of the heat conductor 35 and also urges the bare inner end of the heat conductor in good heat conductive relation with the member 33 which is thermally shielded by insulation 38 from the body 11 which is formed of nonmagnetic material like bronze or brass, for example. As shown in FIG 1, the member 33 and insulation 38 are formed with aligned openings 39 and 40 which communicate With the opening 18 and provide a path of flow for fuel from chamber 14 into the mixing chamber 19 of burner tube 20.

The operation of the burner and safety cut-off apparatus just described is substantially as follows. To start the burner 10 the operating member 26 is pushed upward to move valve 17 to its open position. This permits fluid fuel to flow from chamber 14 and aligned open ings 39, 40 and 18 into the mixing chamber 19. In chamber 19 the gas is mixed with primary air which is admitted through openings 21. The gas mixture flows upward through burner tube 20 and opening 22 at which region the gas mixture is ignited to provide the burner flame. The heat receiving outer end 35" of the heat conductor 35 is heated by the burner flame and heat flows through the heat conductor to the thermomagnetic member 33 in good heat conductive relation therewith. When the temperature of the member 33 comes up to the predetermined level referred to above, it becomes magnetic to establish a magnetic field which constitutes the sole force to hold the permanent magnet 32 in attracted position. When this occurs the operating member 26 may be released and valve 17 will remain in its open position.

If for any reason the burner flame is extinguished, heating of the outer free end 35" of the heat conductor 35 will stop, which in turn terminates the flow of heat through the heat conductor 35 to the thermomagnetic member 33. When the temperature of member 33 drops below the predetermined level, it becomes essentially nonmagnetic and the coil spring 23 will be eflective to cause the valve 17 to move to its closed position and completely shut off flow of fuel to the burner tube 20.

The thermomagnetic member may be formed of chromium manganese antimonide compounds of the form of Mn Cr Sb, for example, which exhibit a ferrimagnetic to anti-ferromagnetic phase transformation with decreasing temperature. When the member 33 is formed of a material of this kind, it is essentially nonmagnetic below a critical temperature referred to as the exchange inversion temperature, which is dependent upon the amount of chromium present. Above the exchange inversion temperature materials of this kind become strongly magnetic. The member 33 may be formed of a material of this kind having an exchange inversion temperature of 150 C., for example, whereby a magnetic field will be established which by itself possesses suflicient strength to attract the permanent magnet 32 from its closed position shown in FIG. 1 against the biasing action of the coil spring 23. When the valve 17 is manually moved to its open position, it will remain in such open position when the member 33 is heated above the exchange inversion temperature and a strong magnetic field is established to hold the permanent magnet 32 in its attracted position against the biasing action of the coil spring 23.

In order to promote rapid heating of the thermomagnetic member 33 above its exchange inversion temperature when the burner flame is initially ignited, the heat conductor 35 is covered with insulation 36 to reduce heat losses and insure effective transfer of heat from the heat receiving end 35" of the heat conductor to the member 33.

If for any reason the burner flame is extinguished, it is desirable to promote rapid lowering of the temperature of the member 33 below its exchange inversion temperature, at which time it becomes essentially nonmagnetic and lacks magnetic properties to hold the valve 17 in its open position. The rate at which the temperature of the member 33 drops is dependent upon the flow of heat from the member 33 to parts of the burner body 11 adjacent thereto. In order to maintain the member 33 above its exchange inversion temperature when the burner flame is being maintained, it is thermally shielded from the body or housing 11 by the insulation 38. At the same time the thermal shielding of the member 33 by the insulation 38 is of such a character that dissipation of heat therefrom will not be impeded, so that the temperature of the member will drop rapidly below the exchange inversion temperature if for any reason the burner flame should be extinguished.

FIG. 2 diagrammatically illustrates a modification of the invention shown in FIG. 1. The parts in FIG. 2 which are similar to the parts in FIG. 1 are designated by the same reference numerals followed by the suffix a. In this modification the thermomagnetic member 33a is imperforate and the inner end 35a of the heat conductor 35a is integral with the member 33a. When valve 17a is in its open position, fuel flows from chamber 14a through a passage 41 to the opening 18a which functions as an orifice through which fuel is discharged into the burner tube 20a. Whereas the body 11 in FIG. 1 is formed from two sectionswhich are threadedly connected together, the body 11a in FIG. 2 comprises two sections which are secured together at 42 by threaded bolts and tightening nuts.

FIGS. 3 and 4 diagrammatically illustrate further modifications of the invention shown in FIGS. 1 and 2. The parts in FIGS. 3 and 4 which are similar to the parts in FIG. 1 are designated by the same reference numerals followed by the suflix b. In FIG. 3 the body 1112 is formed with a fuel inlet 12b and the fuel outlet 43 to which is connected a burner tube 20b, the burner flame of which is maintained at the vicinity of the outer free end 35b" of the heat conductor 35b which is threadedly connected at its inner end 3512 to the thermomagnetic member 33b.

The mechanism for manually moving the valve 17b from its closed position to its open position is omitted from the FIG. 3 embodiment. To start the burner 10b in FIG. 3 the outer free end 35b" of the heat conductor 35b is heated by a torch in any suitable manner. When suflicient heat at an elevated temperature is applied to the outer free end 35b" of the heat conductor 35b by the torch, heat will be rapidly transferred through the heat conductor from 35b to the thermomagnetic member 33b to raise its temperature above the critical temperature, so that it will become strongly magnetic and establish a magnetic field which by itself will attract the permanent magnet 32b and move the valve 17b from its closed position to its open posit-ion. The torch may be employed to ignite the gas mixture issuing from the burner tube 20b to provide the burner flame.

FIG. 4 is similar to the modification of FIG. 3 and differs therefrom by including mechanism for manually moving the valve. In FIG. 4 it will be noted that a cap screwlike the cap screw 25 in FIG. 1 is not employed. The cap screw is eliminated in FIG. 4 by employing a resilient apertured disk 44 which is spring-pressed into an annular groove in the wall of the chamber 28b. In other respects, the operating member 26b, rod 24b, coil spring 30b and washer 31b cooperate in the same manner as the similarly numbered parts shown in FIG. 1 and described above. The body 11b in the modifications of FIGS. 3 and 4 comprises two sections which are threadedly connected together, the bottom section having a passage 45 through which fuel flows from the chamber 14b to the outlet 43.

' FIGS. 5, 6 and 7 are fragmentary sectional views of embodiments like those shown in FIGS. 3 and 4. The parts in FIGS. 5, 6 and 7 which are similar to the parts in FIGS. 3 and 4 are designated by the same reference numerals followed by the suflfixes c, d and e. In FIG. 5 the burner tube 200 is formed of good heat conducting material and functions as the heat conducting member 350. The flange 35c at the lower end of the tube 200 forms the inner end of the heat conductor and is in good heat conductive relation with the thermomagnetic member 330 having a central opening 39c which functions as the orifice through which fuel flows into the lower end of the burner tube 200. The top section of the body 110 takes the place of the cap screw 37 in the embodiment of FIG. 1 and firmly secures in place a body of insulation 380 which thermally shields the member 330 from the top section of the body 110 and also holds the burner flange 35c in good heat conductive relation with the member 33c.

The outer free end 350" of the heat conductor is formed by an upwardly extending metal strip, the lower end of which is fixed to the top part of the burner tube 200 and the upper end of which terminates at the vicinity of the flame.

In the modification of FIG. 6 the heat conductor 35d is in the form of a rod which extends upward within the burner tube 20d. The lower end of the rod 35d is fixed to the thermomagnetic member 33d while the upper end thereof projects upward through the opening 22d and terminates at the vicinity of the flame. In FIG. 6 the member 33d is thermally shielded by insulation 38d from the top section of the body 11d in the same manner shown in FIG. 5 and described above.

The modification shown in FIG. 7 is similar to that of FIG. 5 and differs therefrom in that the burner tube 20e is provided with inner and outer layers of insulating material 36e and 362", respectively.

Each of the modifications of FIGS. 5, 6 and 7 may be of the form shown in FIG. 4 in which mechanism is provided for manually moving the valves 17c, 17d and 17e from their closed to their open positions, or of the form shown in FIG. 3 in which the mechanism for manually moving the valves is omitted.

The permanent magnet 32 in FIG. 1 and similar part in FIGS. 2 to 7 functions as an armature of a thermomagnetically powered operator which is connected to control means, such as the valve sealing means 34 in FIG. 1 and similar part in FIGS. 2 to 7. The control means is biased toward one position and movable toward another position. The thermomagnetically powered operator also includes the member 33 in FIG. 1 and similar part in FIGS. 2 to 7, the member 33 becoming magnetic when its temperature comes up to a predetermined level and becoming nonmagnetic when its temperature drops below the predetermined level. The thermomagnetic member is heat conductively connected to a heat receiving member and adapted when heated to the predetermined temperature level to establish a magnetic field which constitutes the sole force to attract the permanent magnet and hold the armature in an attracted position and maintain the control means at the other position against the bias.

In view of the foregoing, it will now be understood that the body 11 forms the housing of a valve unit having valve means 17 biased to a first flow-preventing position and movable against the bias to a second flow-permitting position. The valve means 17 comprises sealing means 34 and forms part of a movable member that includes permanently magnetized material 32 which is magnetically attracted by means which is only thermomagnetic and comprises structure 33 which becomes magnetic and attracts and holds the movable member to maintain the valve means 17 in the first flow-permitting position when the temperature of the structure 33 comes up to a predetermined level and which becomes substantially nonmagnetic and ineffective to attract said member to maintain said valve means in the flow-permitting position when the temperature of the structure 33 drops below the predetermined level.

The elongated heat conductor 35 forms part of heat receiving means heat conductively connected to the structure 33 which is adapted to be responsive to the heat of fuel burned at the burner tube 20 to render the structure 33 magnetic and operable to attract the movable member to maintain the valve means 17 in the first flow-permitting position and to demagnetize the structure 33 to render the latter ineffective to attract the movable member to maintain the valve means in the first flow-permitting position in response to extinction of the burner.

Although we have shown our invention in connect-ion with safety cut-off apparatus, we do not wish our invention to be limited to the particular arrangements set forth, and we intend in the following claims to cover all modifications which do not depart from the spirit and scope of our invention.

We claim:

1. In a control device for a fluid fuel burner, valve means in the path of fluid flow to said burner, said valve means being biased to flow-preventing position and movable to flow-permitting position with respect to the fluid flow, said valve means forming part of a movable member comprising permanently magnetized material, holding means for magnetically attracting said member to hold said valve means in flow-permitting position against said bias when moved thereto, said holding means comprising only thermomagnetic structure which becomes magnetic and energizes said holding means when the temperature of said structure comes up to a predetermined level and which becomes essentially nonmagnetic and de-energizes said holding means when the temperature of said structure drops below the predetermined level, heat receiving means heat conductively connected to said thermomagnetic structure and adapted to be responsive to the heat of fuel burned at said burner for energizing said holding means in response to burning of said fuel and for deenergizing said holding means in response to extinction of said burner, and a manually movable member cooperable with said valve means and biased from the latter, said manually movable member being movable against its said bias to move said valve means from its flow-preventing position to its flow-permitting position.

2. In a control device for a fluid fuel burner, a valve unit comprising valve means in the path of fluid flow to said burner, said valve means being biased to flow-preventing position and movable against said bias to flowpermitting position with respect to the fluid flow, said valve means forming part of a movable member comprising permanently magnetized material, means for mag netically attracting said member to maintain said valve means in said flow-permitting position against said bias when moved thereto, said magnetic attracting means being only thermomagnetic and comprising structure which becomes magnetic and attracts and holds said member to maintain said valve means in said flow-permitting position when the temperature of said structure comes up to a predetermined level and which becomes substantially nonmagnetic and ineffective to attract said member to maintain said valve means in said flow-permitting position when the temperature of said structure drops below the predetermined level, and heat receiving means heat conductively connected to said structure which is adapted to be responsive to the heat of fuel burned at said burner to render said structure magnetic and operable to attract said member to maintain said valve means in said flowpermitting position and to demagnetize said structure to render the latter ineffective to attract said member to maintain said valve means in said flow-permitting position in response to extinction of said burner.

3. Apparatus as set forth in claim 2 in which said valve unit comprises a housing formed of heat conductive material, said structure being disposed in said housing, and means for thermally shielding at least a part of said structure from said housing.

4. In a control device, a movable member biased to a first position and movable against said bias to a second position, said movable member comprising permanently magnetized material, means for magnetically attracting structure Which becomes magnetic and attracts and holdssaid movable member in said second position when the temperature of said structure comes up to a predetermined level and which becomes substantially nonmagnetic and ineffective to attract said movable member in said second position when the temperature of said structure drops below the predetermined level, and heating means to heat said magnetic attracting means to render the latter magnetic and operable to attract said movable member in said second position, said magnetic attracting means becoming demagnetized and inefiective to attract and hold said movable member in said second position responsive to cessation of heating thereof by said heating means.

References Cited by the Examiner UNITED STATES PATENTS Wittmann 137-65 Lange 236-88 Mantz 158-421 X Ray 251-30 Boyer 236-88 X Ray 158-127 Wittmann 236-88 Holmes Q 251-141 Rhodes et al 251-141 X FREDERICK L. MATTESON, 111., Primary Examiner.

I AM'ES W. WESTHAVER, Examiner. 

2. IN A CONTROL DEVICE FOR A FLUID FUEL BURNER, A VALVE UNIT COMPRISING VALVE MEANS IN THE PATH OF FLUID FLOW TO SAID BURNER, SAID VALVE MEANS BEING BIASED TO FLOW-PREVENTING POSITION AND MOVABLE AGAINST SAID BIAS TO FLOWPERMITTING POSITION WITH RESPECT TO THE FLUID FLOW, SAID VALVE MEANS FORMING PART OF A MOVABLE MEMBER COMPRISING PERMANENTLY MAGNETIZED MATERIAL, MEANS FOR MAGNETICALLY ATTRACTING SAID MEMBER TO MAINTAIN SAID VALVE MEANS IN SAID FLOW-PERMITTING POSITION AGAINST SAID BIAS WHEN MOVED THERETO, SAID MAGNETIC ATTRACTING MEANS BEING ONLY THERMOMAGNETIC AND COMPRISING STRUCTURE WHICH BECOMES MAGNETIC AND ATTRACTS AND HOLDS SAID MEMBER TO MAINTAIN SAID VALVE MEANS IN SAID FLOW-PERMITTING POSITION WHEN THE TEMPERATURE OF SAID STRUCTURE COMES UP TO A PREDETERMINED LEVEL AND WHICH BECOMES SUBSTANTIALLY NONMAGNETIC AND INEFFECTIVE TO ATTRACT SAID MEMBER TO MAINTAIN SAID VALVE MEANS IN SAID FLOW-PERMITTING POSITION WHEN THE TEMPERATURE OF SAID STRUCTURE DROPS BELOW THE PREDETERMINED LEVEL, AND HEAT RECEIVING MEANS HEAT CONDUCTIVELY CONNECTED TO SAID STRUCTURE WHICH IS ADAPTED TO BE RESPONSIVE TO THE HEAT OF FUEL BURNED AT SAID BURNER TO RENDER SAID STRUCTURE MAGNETIC AND OPERABLE TO ATTRACT SAID MEMBER TO MAINTAIN SAID VALVE MEANS IN SAID FLOWPERMITTING POSITION AND TO DEMAGNETIZE SAID STRUCTURE TO RENDER THE LATTER INEFFECTIVE TO ATTRACT SAID MEMBER TO MAINTAIN SAID VALVE MEANS IN SAID FLOW-PERMITTING POSITION IN RESPONSE TO EXTINCTION OF SAID BURNER. 